What is Flexible Shaft Couplings

Flexible shaft couplings connect two shafts, end-to-end and in the same line, causing both to rotate at the same speed. They also flex to compensate for misalignment and movement between shafts. This compensation is crucial because perfect alignment of two shafts is extremely difficult and rarely achieved. There are two types of misalignment: angular and parallel. Most flexible shaft couplings also accommodate axial movement, or end float, of the shafts.

Depending on the type, most flexible shaft couplings can accommodate from 1/4 of a degree to 4 degrees of misalignment. Low speed couplings are aligned to 0.001 in/in (3.5 seconds) and for high speed, they are aligned even tighter at 0.0005 in/in (1.75 minutes). Maximum parallel misalignment can range from a few hundredths of an inch to over an inch.

Other Functions of Flexible Shaft Couplings:

Every Type of  flexible shaft couplings

• Mechanically Flexible: obtain flexibility from a clearance between components that allows rolling or sliding. They require lubrication unless a moving part is made from a self-lubricating material.
• Elastomeric Element: obtain flexibility from shear or compression of a resilient polymer material, like rubber or plastic. The material may be mechanically interlocked, bolted, clamped, or molded to the hubs. They offer better shock and vibration damping than other types but are subject to operating temperature limitations.
• Metallic Element: obtain flexibility from the flexing of thin metallic discs or diaphragms.
• Miscellaneous: obtain flexibility from a combination of mechanisms mentioned above.

Flexible Shaft Couplings

Choosing the Right Flexible Shaft Couplings for Your Application

Flexible Shaft Couplings provide torque transmission while helping to improve machine performance and life, but using the wrong type of coupling can impede mechanical performance. Flexible shaft Couplings that are too rigid can create excessive bearing loads that can impact performance and life.  Flexible shaft Couplings with backlash or that “wind-up” in applications with changing speeds can limit a machine’s operating speed and performance. Incorrect installation or using shaft couplings outside their recommended ratings can also cause issues. 
 Primary considerations for properly selecting a flexible shaft couplings include torque capacity, motion profile, maximum RPM, flexible shaft couplings, shaft sizes, and the type and amount of misalignment. Once installed, a flexible shaft couplings should be relatively easy to connect and disconnect for inspection, as needed.